ETX power input question

I normally use my ETX 90 via the 12v power input plugged into a wall, and once in a while I use my power tank. Today I went to a remote site for terrestrial viewing and I didn't feel like bringing my power tank, and there were no wall plugs to use, so I put in some batteries. Now I know the scope can be finicky based on which power input you use, so I don't like to switch around alot. My question is this: If I leave the batteries in, and still use the 12v input - will the scope detect battery use or the 12v input? I have the drives trained for a wall outlet and don't want to retrain for batteries. Thanks for any help!